Utilization of the emergency department by kidney transplant recipients: a retrospective cohort study from a high-volume transplant center

Background: This study aims to assess the trends of emergency department (ED) visits among kidney transplant recipients in a high-volume transplant centre. Methods: This retrospective cohort study targeted patients who underwent renal transplantation at a high-volume transplant centre from 2016 to 2020. The main outcomes of the study were ED visits within 30 days, 31–90 days, 91–180 days, and 181–365 days of transplantation. Results: This study included 348 patients. The median (interquartile range) age of patients was 45.0 years (30.8, 58.2). Over half of the patients were male (57.2%). There was a total of 743 ED visits during the first year after discharge. 19% (n=66) were considered high-frequency users. High-volume ED users tended to be admitted more frequently as compared to those with low frequencies of ED visits (65.2% vs. 31.2%, respectively, P<0.001). Conclusion: As evident by the large number of ED visits, suitable coordination of management through the ED remains a pivotal component of post-transplant care. Strategies addressing prevention of complications of surgical procedures or medical care and infection control are aspects with potential for enhancement.

Since the first successful renal transplant from a healthy live donor to their identical twin over half a century ago, transplant surgery has emerged as a well-established treatment for end-stage renal disease [1,2] . The introduction of effective immunosuppressants has led to a significant increased life expectancy of organ transplant recipients [3] . Due to the significant increase of the transplant recipient population, there is an increased amount of emergency physicians who are faced with caring for this complex population [4] . These complex patients may present with underlying medical conditions that may be associated with their transplant surgeries or immunosuppressive therapies.
In the literature, there are several comprehensive studies evaluating hospital re-admissions and ED visits among renal transplant recipients [5][6][7] . However, there is limited data on the usage of the ED post-renal transplantation in Saudi Arabia and the Middle East. Thus, this study aims to assess the trends of ED visits among kidney transplant recipients in a high-volume transplant centre.

Materials and methods
This retrospective cohort study targeted all adult patients, aged 14 years and older, who underwent renal transplantation at our hospital from 1 January 2016, to 31 March 2020. Patients who had a second renal transplant, or a renal transplantation in a different hospital and followed-up at our hospital, were excluded.

HIGHLIGHTS
• Kidney transplant most often visit the emergency department (ED) 6-12 months after discharge. • Among kidney transplant recipients, high-volume ED users are admitted significantly more than low-volume users. • High-volume visits are significantly associated with several conditions, such as pneumonia, cardiac dysrhythmias, and urinary tract infections.
The data were collected using the BESTCare system (ezCareTech, South Korea). This study included all patients complying with the inclusion criteria in the study period. The main outcomes of this study were ED visits within 30 days, 31-90 days, 91-180 days, and 181-365 days of transplantation. Demographic data, including age, sex, BMI, and co-morbidities were collected. The BMI of each patient was categorized into four groups: <18.5 kg/m 2 as underweight, 18.5-24.9 kg/m 2 as normal, 25.0-29.9 kg/m 2 as overweight, ≥ 30 kg/m 2 as obese based on the WHO general population classification [8] . The transplantationrelated data collected were donor condition, cold ischaemia time, delayed graft function, postoperative haemodialysis, postoperative ICU admission, and length of stay. ED visit parameters consisted of visit intervals, overall number of ED visits, whether the patient is a high-volume user (four or more annual visits) or not, presenting complaints, and ED admission decisions [9] .
Data analysis was performed using RStudio (R version 4.1.1). We used frequencies and percentages to express categorical variables and median and interquartile ranges to present numerical variables. The statistical differences between highvolume and low-volume users of ED were explored using a Pearson's χ 2 test or a Fisher's exact test for categorical variables or a Wilcoxon rank sum test for numerical variables. Statistical significance was considered at P < 0.05. This study is registered on the research registry with a unique identifying number: researchregistry8691 [10] . This study has been reported in line with the STROCSS criteria [11] . The Institutional Review Board of King Abdullah International Medical Research Center, Ministry of National Guard -Health Affairs, Riyadh, Kingdom of Saudi Arabia, approved the study, with approval number RC20/204/R.

Results
Demographic and end-stage renal disease (ESRD)-related characteristics of patients Three hundred forty-eight patients were included in this study. The median (interquartile range) age of patients was 45.0 years (30.8, 58.2). Over half of the patients were male (57.2%). Almost one-third of patients were overweight (32.6%) and obese (32.6%). The most common causes of ESRD were diabetes mellitus (35.1%), hypertension (30.2%), and glomerular nephritic syndrome (14.3%). The majority of patients underwent haemodialysis at the time of ESRD (82.3%). Living donors represented 77.8% of patients with 0 human leukocyte antigen mismatch number (80.6%). More details about patients' characteristics are listed in Table 1.
There was a total of 743 ED visits during the first year after discharge. During the year, 20.1% (n = 70) of patients visited the ED once, 14.1% (n = 49) visited the ED twice and 8.3% (n = 29) visited ED three times. Mean number of ED visits was 3.4 3.2. During the first 30 days after discharge, 37.9% (n = 132) of renal transplant (RT) patients visited the ED. Moreover, 23.6% (n = 82) utilized the ED in the interval of 31-90 days after discharge, 23% (n = 80) in the interval of 91-180 days after discharge, and 36.8% (n = 128) in the interval of 181-365 days after discharge. Of all RT patients that visited the ED in the first year, 19% (n = 66) were considered high-frequency users. Of all ED visits, 29.8% (n = 222) led to re-admissions. 52.7% percent of RT patients that visited the ED within the first 30 days after discharge were readmitted. 56.1% that visited within the interval of 31-90 days were readmitted. 65% that visited within the interval of 91-181 days were readmitted. 46.9% that visited within the interval of 181-365 days were readmitted.

Factors associated with being a high-volume user
High-volume usage of the ED did not differ significantly based patient's demographic and ESRD-related data. However, highvolume ED users tended to be admitted more significantly compared to those with low frequencies of ED visits (65.2% vs. 31.2%, respectively, P < 0.001), as shown in Table 2. Notably, comorbid conditions were not significantly different between high-volume and low-volume users (Table 3). Nevertheless, the proportions of presenting complaints were significantly higher among high-volume users compared to their peers; these included abdominal pain (68.2% vs. 35.8%, P < 0.001), infectious symptoms (60.6% vs. 19.1%, P < 0.001), urinary symptoms  Table 3. As shown in Table 4, the compliance rate for outpatient nephrology visits ranged between 94% at first 30 days to 95.4% at 31-90 days. Furthermore, Table 5 shows the use of immunosuppression drugs among the patients in our sample.

Discussion
This study was conducted at our centre over a period of 3 years and 3 months, and included a total of 348 renal transplant Table 2 The association between demographic and ESRD-related data and the intensity of ED visits.
A high-volume user recipients. It aims to describe ED visits by these patients focusing on rates, complaints, co-morbidities, re-admissions and ability of the ED to handle such cases. While the length of stay after transplant was roughly the same for all patients, and delayed graft function was seen only in a small population (6.9%), the number and causes of visits were variable and numerous. Male predominance was seen, with 57.2% males and 42.8% females. This is similar to the American multicenter study, where male constituted around 63.1% [12] . Cumulatively, this may suggest gender related complaints and complications. Though the long-term survival rate for kidney transplant recipients is more in females as compared to males in the Taiwan study, no significance difference was found in our study between males and females in regard to the frequency of ED use [13] . In addition, no significant association of obesity could be seen in the ED visits, as the ratio of normal BMI, overweight, and obese patients was almost the same. Moreover, no association was found with BMI category, which is in accordance with other studies [12][13][14] .
In our population, all the patients who underwent renal transplants at our centre visited the ED at least once during the first-year post-renal transplant. Interestingly, these findings differ from a study that was done in Granada, where less than 50% of the population utilized the ED services during the first-year posttransplantation [15] . This stresses the importance of more scheduled outpatient visits for renal transplant patients, better analgesia, clear discharge instructions, and further evaluation of their concerns [16] . 37.9% of our patients presented within the first month of discharge. This data are similar to a study conducted in the United States in 2014 [17] . They reported that 30.5% of their patients visited the ER within a month of after discharge [17] . However, there is a study conducted in Cleveland which has differing data from our study [18] . They reported only 12% of their patients visiting the ED within a month of transplantation [18] . Furthermore, they reported that the most common cause of ED visits was complications of therapeutic procedures (implants, grafts) whereas we reported abdominal pain as the most common cause [18] . These interesting findings shows a variation in the trend of ED utilizations, which may be due to a potential increased incidence of early post-transplant complications in our population, further studies on this manner are warranted. The rates of ED visits were 23.6% in 31-90 days, 23% in 91-180 days and 36.8% in 181-365 days. An increase in the number of visits by kidney transplant recipients is seen from 6 to 12 months after discharge. This percentage is similar to the Cleveland study, showing a 40% utilization during the same period [18] . As described in their paper, the increased incidence may be because patients prefer the ED as a suitable care unit over an extended period. Thus, there is a need of a proper and sufficient ED setup. In our study there was a total of 29.8% patients that were readmitted owing to their conditions and complications. This is contrary to the Cleveland research, where half the patients had to be readmitted [18] .
Gastrointestinal symptoms and infectious symptoms were the main causes of ED visits, which is consistent with other studies [15,19,20] . These remain the major reasons for visits due to regular use of immunosuppressive drugs after transplant, which may increase the incidence of urinary tract infections and gastrointestinal symptoms [21] . This data indicates the need to have protocols for the ED staff for dealing with post-kidney transplants patients and their most common presentations.
Co-morbidities such as diabetes and heart failure are an important risk factor of post-transplant complications, graft rejection and mortality [16,22] . Nevertheless, there was no association in our population between having co-morbidities and being a frequent ED user. In addition, the high influx of ED visits may be due to patients' concerns regarding their health posttransplant, this is further shown by a study done by Tucker et al. [23] who reported that 74% of their patients visiting the ED were concerned about quality of life, co-morbidities, and kidney related issues.
This study has several strengths and limitations. One of the strengths is that this study collected data using a reliable and efficient electronic health record system, which allowed for the easy retrieval of data for analysis. Another strength is this study's focus on a specific and understudied population of renal transplant recipients in Saudi Arabia and the Middle East, which provides valuable information on the trends of ED visits in this region. However, this study also has limitations. One of the limitations is that this study only includes data from a single high-volume transplant centre, which may limit the generalizability of the findings to other transplant centres. Additionally, this study is limited by its retrospective design, which makes it difficult to establish causality between variables.
As another limitation of our study, we acknowledge the lack of data from our specific region to serve as a direct comparison to our findings. While we compared our results to studies conducted in the United States of America, differences in healthcare infrastructure and practices may have influenced the presentation of post-op renal transplant patients in our region. In addition, we acknowledge that we did not report the compliance rate of outpatient nephrology visits for high-volume users and low-volume users separately. This is an important factor that could potentially affect the rate of ED utilization and should have been recorded. We hope that our study serves as a stimulus for further research in our region to address these limitations and provide more comprehensive data on this important topic. Finally, the study is limited by the small sample size, which may limit the ability to detect significant differences between groups.

Conclusion
The regular visits to the ED and utilization of its facilities warrants establishment of a protocol for post-renal transplantation patients. ED staff should be aware of and trained to deal with these cases, and the department itself should be up to date. Care protocols should be formed and followed, and specific interventions need to be introduced. There is also a need for coordination between the ED and nephrology units. The number of renal transplant recipients is increasing with better transplant facilities. The authors aim to introduce awareness regarding this issue, leading to proper patient care and better healthcare system for patients and medical staff alike, along with mitigating the preventable factors that could increases the financial burden on the healthcare system.

Ethics approval
IRB approval was waived for this study.

Consent to participate
Not applicable.

Source of funding
This study did not receive funding from any source.